Improving the construction of the DBM over approximation of the state spce of real-time preemptive systems

We present in this paper an algorithm allowing an efficient computation of the tightest DBM over-approximation of the state space of preemptive systems modeled by using Time Petri Nets with inhibitor arcs. First of all, we propose an algorithm that reduces the effort of computing the tightest DBM over-approximated graph. For this effect, each class of this graph is expressed as a pair (M, D), where M is a marking and D is the system of all DBM inequalities even the redundant ones. We thereby make it possible to compute the system D straightforwardly in its normal form, without requiring to compute the intermediary polyhedra. Hence, we succeed to remove the errors reported in the implementation of other DBM approximations. Then we show that by relaxing a bit in the precision of the DBM approximation, we can achieve to construct more compact graphs while reducing still more the cost of their computation. We provide for this abstraction a suitable equivalence relation that contract yet more the graphs. The experimental results comparing the defined constructions with other approaches are reported

Time Analysis of the State Space of Real-time Preemptive Systems

We present in this paper an algorithm making it possible an efficient time analysis of the state space of preemptive real time systems modeled using Time Petri Nets with inhibitor arcs. For this effect, we discuss how to determine from the reachability graph linear and quantitative properties of the remote model. Then, we propose an algorithm to compute an approximation of the minimal and the maximal time distances of any firing sequence. Contrarily to other techniques, our algorithm enjoys a linear complexity time cost and can be performed on the fly when building the reachability graph without requiring to extend the original model with observers

Distributed architecture for resource description and discovery in the IoT

Nowadays, the Internet of Things (IoT) creates a vast ecosystem of intelligent objects interconnected via the Internet, allowing them to exchange information and to interact. This paradigm has been extended to a new concept, called the Web of Things (WoT), considering that every physical object can be accessed and controlled using Web-based languages and protocols, such as: the CoAP protocol which is becoming the most accepted and suitable protocol in this context. Moreover, the architectures currently proposed for the creation of IoT environments lack efficient and standard support for the discovery, selection and composition of IoT services and their integration in a scalable and interoperable way. To overcome this, in this work, we propose a hybrid and distributed CoAP-based architecture, considering all these aspects by combining the Fog Computing paradigm and structured P2P overlay networks. Furthermore, we describe the different components of our architecture and explain the interaction between them

Toward Specifying Multimedia Requirements Using a New Time Petri Net Model

In this paper, we define a model dedicated to the specification of multimedia applications called Pre-emptive Time Petri Nets with synchronizing transitions (STPTPN) as an extension of T-time Petri nets where time is associated with transitions. The model is proposed in the general purpose to model a large scale of multimedia requirements. Thus, resource requirement issues are discussed in this paper, and addressed in the model. To deal with, resources are modelled as special places using a new mechanism called “pre-emptor hyperarc” which lets a transition be “resource strongly-enabled”, “resource-violated” or “resource-violating”. Moreover, two additional mechanisms are considered: A time suspension mechanism uses inhibitor arcs associated with stopwatches and synchronization mechanisms allow the simultaneous firing of a set of transitions (called Rendezvous), according to different schemes. Compared to other existing models, our model is provided with an adapted semantic, designed to represent clearly and accurately time requirements, as well as the complex resource-pre-empting mechanisms that are observed in multimedia systems

Dealing with complex routing requirements using an MCDM based approach

The last decade has witnessed an ever-growing user demand for a better QoS (Quality Of Service) and the fast growth of connected devices still put high pressure on the legacy network infrastructures. To improve network performances, better manage the resources and have a greater control over traffic transmission, intelligent routing procedures are increasingly demanded. Modern applications in the dynamic context of new emerging networks have their own routing requirements, in terms of set of metrics to consider, their importance and thresholds to respect. The objective of this work is to design an approach based on MCDM (Multi-Criteria Decision Making) to decide complex routing problems when assuming threshold constraints on metrics. We give the mathematical framework to capture such requirements and to decide the routing. A case study is presented to advocate the benefit of using our approach

Dealing with complex routing requirements using an MCDM based approach

The last decade has witnessed an ever-growing user demand for a better QoS (Quality Of Service) and the fast growth of connected devices still put high pressure on the legacy network infrastructures. To improve network performances, better manage the resources and have a greater control over traffic transmission, intelligent routing procedures are increasingly demanded. Modern applications in the dynamic context of new emerging networks have their own routing requirements, in terms of set of metrics to consider, their importance and thresholds to respect. The objective of this work is to design an approach based on MCDM (Multi-Criteria Decision Making) to decide complex routing problems when assuming threshold constraints on metrics. We give the mathematical framework to capture such requirements and to decide the routing. A case study is presented to advocate the benefit of using our approach

Validation d'un modèle basée sur les RdPT pour la spécification et l'analyse des systèmes temps réel complexes : Application aux systèmes multimédias

Nowadays, parallel systems are more and more used in the computing world. ; they are characterized by their power and complexity. An important class of computing systems is that of real-time systems.Real-time systems are systems whose behavior must satisfy hard time constraints. They are generally characterized by complex interactions with their environment; they must therefore necessarily be reliable. This includes highly reactive systems whose decisions can have immediate and irreversible consequences on goods and men. Their fields of application are wide, ranging from domestic applications such as household heating and cooking control systems, to the most complex and critical systems such as avionics control systems, nuclear, industry and telecommunications.To verify the reliability of such systems, formal methods have been widely considered and stand an important step in their development process. It starts with the proposal of a mathematical model capable of faithfully describing their temporal behavior and follows the proposal of analysis techniques adapted to this model, allowing to verify the qualitative and quantitative properties of these systems.Subsequently, the subject of our work is to design a framework related to the specification and to the verification of multimedia applications whose complex requirements partly take up the needs of real-time systems. The proposals that we develop in this thesis could resonate with real-time applications in the broad sense, due to the fact that they allow to define a unified formal framework allowing the management of a large part of theissues raised in such systems.De nos jours, les systèmes parallèles sont de plus en plus répandus dans le monde informatique ; ils sont caractérisés par leur puissance et leur complexité. Une classe importante des systèmes informatiques est celle des systèmes temps réel.Les systèmes temps réel sont des systèmes dont le comportement doit satisfaire des contraintes temporelles strictes. Ils sont en général caractérisés par des interactions complexes avec l'environnement ; ils doivent par conséquent nécessairement être fiables. Il comprennent les systèmes hautement réactifs dont les décisions peuvent avoir des conséquences immédiates et irréversibles sur des biens et des hommes. Leurs domaines d'application est large, allant de la simple utilisation domestique tels que les systèmes de contrôle des chauffages et des cuisinières, jusqu'aux systèmes les plus complexes et les plus critiques tels que les systèmes de commande de l'avionique, le nucléaire, l'industrie et les télécommunications. Pour vérifier la fiabilité de tels systèmes, les méthodes formelles ont été largement utilisées et constituent une étape importante dans leur processus d'élaboration. Cela commence par la proposition d'un modèle mathématique capable de d'écrire fidèlement leurs comportements temporels et s'en suit la proposition de techniques d'analyse adaptées ç ce modèle, permettant de vérifier qualitativement et quantitativement les propriétés de ces systèmes.Par la suite, nous inscrivons notre travail dans un cadre particulier relatif à la spécification et à la vérification des applications multimédias dont les exigences complexes résument en partie les besoins des systèmes temps réel. Les propositions que nous développons dans cette thèsepourraient trouver écho au près des applications temps réel au sens large, du fait qu'elles permettent de définir un cadre formel unifié permettant la prise en charge d'une grande partie des problématiques posées dans ce type de systèmes